Highly accurate location of the leading and trailing edges of pulsed RF signals in required in many applications. For instance, in position determining receivers, the accuracy of the position determination depends on the precise measurement of the time of arrival of pulsed RF signals. Prior art techniques have relied on logging element, typically a log amplifier, to linearize the output of a square law detector so that a delayed channel can be compared to an attenuated channel to accurately locate the leading edge of an RF pulse. The accuracy with which the output of the detector is linearized severely limits the accuracy of the apparatus and demands careful custom matching of the detector and amplifier. Combined with requirements of increased dynamic range, larger ranges of rise time and pulse duration and reduced power consumption and size, these considerations have rendered techniques inadequate.